The invention relates to a travel measuring system, for detecting a control position of one body relative to another, as defined hereinafter. A travel measuring system is already known in which one part of the system is connected to one of the bodies and another part of the system is connected to the other body, and the control position of one body relative to the other can be measured.
The known travel measuring system is a so-called inductive travel measuring system. One part of the system includes an armature, which is preferably of soft iron, and the other part of the system includes a coil. The coil must be markedly longer than a travel distance to be measured, and the armature must likewise be markedly longer than the travel distance. The result is a travel measuring system having a very long total length. The coil plus the armature are more than twice as long as the travel distance to be measured. The armature influences an inductance of the coil. The inductance of the coil can be used as a standard for the control position of the one body relative to the other. The farther the armature plunges into the coil, the greater does the inductance of the coil become.
In another known travel measuring system, the coil is moved relative to an electrically conductive material. The more the coil plunges into the electrically conductive material, the lower does the inductance of a coil become. Once again, the inductance of the coil is a standard for the control position of one body relative to the other. Openings spaced mutually apart may be provided in the electrically conductive material. Once again, the coil and the electrically conductive material must be longer than the travel distance to be measured. The result is a considerable physical length, which in the extended state is markedly more than twice as long as the travel distance to be measured.
Accordingly, both known travel measuring systems are substantially longer physically, particularly in the extended state, than the travel distance to be measured, so that only in the rarest cases is it possible to build the known travel measuring systems into a cylinder, particularly a cylinder of a shock absorber.